Logs one machine at a time

Guide and demo one machine time:
Set a key in your session that you store in the database in the user table:

Table User:

– user_id
– username
– password
– token

On Login:

– Create random token, set for that user in database and create a session have value is that token:– UPDATE user SET token=’MyRandomToken’ WHERE username=’username’ and password=’password’;– $_SESSION[‘login_token’] = ‘MyRandomToken’;

On every page:

– SELECT user_id, username, token FROM user WHERE token=’$_SESSION[‘login_token’]’;
– If not found then the logiin token is no longer valid.

This makes sure that a login expires automatically if there is a newer login. There can be only one logged in user per account at any time.

UPDATE OTHER SOLUTION

If you want to prevent a second login then using a timestamp that you update on every page is the best solution:

If a row was found then the account exists and the login is not blocked by another login. You might want to split that into two queries (first check login, then check last access) to give a better error message for failed logins, otherwise it’s either “account does not exist” or “blocked”.